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New videos from Khan Academy 2020-01-09T00:25:39.416508
Actualizado: hace 1 hora 37 mins

Think you know van Gogh? The Potato Eaters

Jue, 2020-01-09 00:25
A conversation with Dr. Beth Harris and Dr. Steven Zucker in front of Vincent van Gogh, The Potato Eaters, 1885, oil on canvas, 82 x 114 cm (Van Gogh Museum, Amsterdam, Vincent van Gogh Foundation).

Introduction: How to use this unit

Mar, 2020-01-07 04:58
This video tells you how to best use this unit.

What does the music of heaven sound like?— St Cecilia in New Spain

Mar, 2019-12-31 13:26
Andrés de Concha, St. Cecilia, 1590, oil on wood (Museo Nacional de Arte, Mexico City, Mexico) A conversation with Dr. Beth Harris and Dr. Lauren Kilroy-Ewbank.

Behind the icon, Dorothea Lange's Migrant Mother

Lun, 2019-12-30 22:48
Dorothea Lange, Migrant Mother, Nipomo California, 1936, printed later, gelatin silver print, 35.24 x 27.78 cm (Los Angeles County Museum of Art, PG.1997.2), a Seeing America video. Speakers: Eve Schillo, Assistant Curator, Los Angeles County Museum of Art and Steven Zucker

Magnetic effects of electric current: CBSE board practice

Sáb, 2019-12-28 14:01
Prepare for class 10 CBSE exam for the chapter Magnetic Effects by recalling the concepts of hand rules, generators, and motors.

Electricity class 10 numerical: CBSE board practice

Sáb, 2019-12-28 14:01
Prepare for class 10 CBSE exam for the chapter Electricity by revising difficult board-type numerical questions.

Beyond the Great Wave — Hokusai at 90

Mié, 2019-12-18 22:59
The great Japanese master Hokusai expresses a sense of a life well-lived in these two paintings — of a woodcutter and a fisherman. A conversation with Dr. Frank Feltens, The Japan Foundation Assistant Curator of Japanese Art, Freer Gallery of Art and Dr. Beth Harris, in front of Katsushika Hokusai, Fisherman, 1849, ink and color on silk, 113 x 39.6 cm and Woodcutter, 1849, ink and color on silk, 113.6 × 39.6 cm (Freer Gallery of Art and Arthur M. Sackler Gallery, Smithsonian Institution, gift of Charles Lang Freer in 1920, F1904.181 and 1904.182)

Queen or goddess?

Mié, 2019-12-18 18:34
Queen Sembiyan Mahadevi as the Goddess Parvati, Chola Dynasty (reign of Queen Sembiyan Mahadevi), 10th century, bronze, 107.3 x 33.4 x 25.7 cm (Purchase — Charles Lang Freer Endowment, Freer Gallery of Art and Arthur M. Sackler Gallery, Smithsonian Institution, F1929.84) Speakers: Dr. Emma Natalya Stein, Curatorial Fellow for Southeast Asian Art, Freer Gallery of Art and Arthur M. Sackler Gallery, Smithsonian Institution

Covalent bonds

Dom, 2019-12-15 22:13
Covalent bonds involve the sharing of electron pairs between atoms. Electron pairs shared between atoms of equal or very similar electronegativity constitute a nonpolar covalent bond (e.g., H–H or C–H), while electrons shared between atoms of unequal electronegativity constitute a polar covalent bond (e.g., H–O).

Metallic bonds

Dom, 2019-12-15 22:13
Metallic bonds result from the electrostatic attraction between metal cations and delocalized electrons. The nature of metallic bonding accounts for many of the physical properties of metals, such as conductivity and malleability.

Ionic bonds

Dom, 2019-12-15 22:13
Ionic bonds result from the electrostatic attraction between oppositely charged ions, which form when valence electrons are transferred from one atom to another.

Valence electrons and ionic compounds

Dom, 2019-12-15 22:13
When forming ions, elements typically gain or lose the minimum number of electrons necessary to achieve a full octet. For example, fluorine has seven valence electrons, so it is most likely to gain one electron to form an ion with a 1- charge. We can use this method to predict the charges of ions in ionic compounds.

Introduction to electron configurations

Sáb, 2019-12-14 01:23
Electron configurations describe where electrons are located around the nucleus of an atom. For example, the electron configuration of lithium, 1s²2s¹, tells us that lithium has two electrons in the 1s subshell and one electron in the 2s subshell.

CBSE board practice: Lenses & mirrors

Vie, 2019-12-13 11:25
Let's practice recalling important aspects of mirrors & lenses

Worked example: Calculating mass percent

Vie, 2019-12-13 00:02
To calculate the mass percent of an element in a compound, we divide the mass of the element in 1 mole of the compound by the compound's molar mass and multiply the result by 100.

Worked example: Determining an empirical formula from combustion data

Jue, 2019-12-12 00:57
In combustion analysis, an organic compound containing some combination of the elements C, H, N, and S is combusted, and the masses of the combustion products are recorded. From this information, we can calculate the empirical formula of the original compound.

Worked example: Calculating molar mass and number of moles

Mié, 2019-12-11 17:10
The molar mass of a substance is the mass in grams of 1 mole of the substance. As shown in this video, we can obtain a substance's molar mass by summing the molar masses of its component atoms. We can then use the calculated molar mass to convert between mass and number of moles of the substance.

Average atomic mass

Mié, 2019-12-11 17:10
The average atomic mass (sometimes called atomic weight) of an element is the weighted average mass of the atoms in a naturally occurring sample of the element. Average masses are generally expressed in unified atomic mass units (u), where 1 u is equal to exactly one-twelfth the mass of a neutral atom of carbon-12.

Key features of graphs — Harder example

Mié, 2019-12-11 02:03
Watch Sal work through a harder Key features of graphs problem

Percents — Harder example

Mié, 2019-12-11 02:03
Watch Sal work through a harder Percents problem.

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