Science STAAR TEKS

A scientist spilled a few drops of dilute hydrochloric acid (HCl) on a lab table. For safety purposes, the scientist sprinkled some baking soda (NaHCO₃) onto the spill. Which observation would provide the best evidence that a chemical reaction occurred?

• The baking soda and hydrochloric acid combined, and bubbles formed.

• The baking soda absorbed the hydrochloric acid.

• Some of the baking soda dissolved in the hydrochloric acid.

• The hydrochloric acid evaporated, leaving only the baking soda.

Tags

NGSS.MS-PS1-2

The model of the periodic table below shows the locations of four elements. A student is asked to identify an element that is a pale-yellow brittle solid and does not conduct electricity. At which location in this periodic table would the element most likely be found?

• 1

• 2

• 3

• 4

During an investigation, a student combined the two clear, colorless solutions shown below. The student observed that the temperature changed from 25°C to 23°C when the solutions were combined and that a white substance rapidly formed and settled to the bottom of the container. What most likely happened to produce these results?

• One of the orginal compounds came out of solution

• The solutions reacted chemically

• Some of the water frose into ice crystals

• Rapid evaporation of water occurred, leaving a solid

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?

• The shape of the coal changes

• Oxygen is present

• A new substance is produced

• Coal is made up of more that one element

Tags

NGSS.MS-PS1-2

Some students are using samples of different substances for a lab investigation. They plan to observe the physical properties of each substance and record their observations in a table like the one below. Which of the substances observed are elements?

• S, Fe, O, Sr, and Al

• S, O, and LiF

• NO, O,and LiF

• NO,Fe,Sr,and Al

Tags

NGSS.MS-PS1-1

What is the difference between the number of electrons in an atom of selenium, Se, and the number of electrons in an atom of aluminum, Al?

• 21

• 3

• 51.989

• 105.953

Four students were given a list of compounds and asked to identify which ones are organic. Which student correctly identified the organic compounds in the list?

• Student K

• Student L

• Student M

• Student N

Tags

NGSS.HS-LS1-6

Students in a science class prepared flashcards so that they could quiz one another about the arrangement of the periodic table. One of the flashcards contained information about two elements, Element L and Element M. The students had to use the information on the flashcard to determine possible positions of the two elements on a blank periodic table. Which periodic table has the elements placed in locations that match the information on the flashcard?

• 
• 
• 
• 

Tags

NGSS.MS-PS1-1

How many protons, neutrons, and electrons are present in an atom of hafnium, Hf, with a mass number of 178?

• 72 protons, 178 neutrons, 106 electrons

• 72 protons, 106 neutrons, 72 electrons

• 178 protons, 250 neutrons, 72 electrons

• 106 protons, 72 neutrons, 106 electrons

Tags

NGSS.MS-PS1-1

Tin, Sn, is a soft white metal. It has a low melting point compared with other metals. Tin is widely used as a coating for cans of food. Which statement accurately describes atoms of tin?

• Tin atoms have 50 protons.

• Tin atoms have five valence electrons.

• Tin atoms have 119 neutrons.

• Tin atoms have 68 electrons.

Tags

NGSS.MS-PS1-1